package com.dzsw.netty.basic.nio;

import com.google.common.base.Strings;

import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.util.Arrays;

/**
 * Scattering：将数据写入到buffer时，可以采用buffer数组，依次写入  [分散]
 * Gathering: 从buffer读取数据时，可以采用buffer数组，依次读
 */
public class ScatteringAndGathering {

    public static void main(String[] args) throws Exception {
        //使用 ServerSocketChannel 和 SocketChannel 网络
        ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
        InetSocketAddress inetSocketAddress = new InetSocketAddress(7000);
        //绑定端口到socket ，并启动
        serverSocketChannel.socket().bind(inetSocketAddress);
        //创建buffer数组
        ByteBuffer[] byteBuffers = new ByteBuffer[2];
        byteBuffers[0] = ByteBuffer.allocate(5);
        byteBuffers[1] = ByteBuffer.allocate(3);
        // 等客户端连接(telnet)
        SocketChannel socketChannel = serverSocketChannel.accept();
        int messageLength = 8;   // 假定从客户端接收8个字节
        // 循环的读取
        while (true) {
            int byteRead = 0;
            while (byteRead < messageLength) {
                long l = socketChannel.read(byteBuffers);
                byteRead += l; // 累计读取的字节数
                System.out.println(" ---------------------- start ------------------------");
                System.out.println(Strings.lenientFormat("\n------------------ byteRead = %s----------------------", byteRead));
                // 使用流打印, 看看当前的这个buffer的position 和 limit
                Arrays.asList(byteBuffers).stream().map(buffer -> {
                    String str = Strings.lenientFormat("position = %s, limit = %s, capacity = %s",
                            buffer.position(), buffer.limit(), buffer.capacity());
                    return str;
                }).forEach(System.out::println);
            }
            // 将所有的buffer进行flip
            Arrays.asList(byteBuffers).forEach(buffer -> buffer.flip());
            // 将数据读出显示到客户端
            long byteWirte = 0;
            while (byteWirte < messageLength) {
                long l = socketChannel.write(byteBuffers);
                byteWirte += l;
            }
            //
            StringBuilder sb = new StringBuilder();
            Arrays.stream(byteBuffers).forEach(buff -> {
                buff.rewind();
                while(buff.hasRemaining()) {
                    sb.append((char)buff.get());
                }
            });
            // 将所有的buffer 进行clear
            Arrays.asList(byteBuffers).forEach(buffer -> {
                buffer.clear();
            });
            System.out.println(Strings.lenientFormat("byteRead = %s, byteWirte = %s, messageLength = %s, msg = %s",
                    byteRead, byteWirte, messageLength, sb.toString()));
            System.out.println(" ---------------------- end ------------------------");
        }
    }
}
